This application is a 35 USC 371 application of PCT/DE 00/02736 filed on Aug. 12, 2000.
1. Field of the Invention
The invention relates to a fuel injection valve having a valve body, having a control pressure chamber that is disposed inside the valve body and is closed at one end by an actuating part, which is for an injector needle and can be moved in the control pressure chamber between a closed position and an open position, having an inlet into the control pressure chamber, and having an outlet from the control pressure chamber which is controlled by a control valve.
2. Description of the Prior Art
A control valve of this kind has been disclosed, for example, by DE 197 27 896 A1 and is used to cause an injector needle of the injection valve to open in order to inject fuel into a cylinder of an internal combustion engine.
The injector needle is permanently acted upon by an opening pressure which strives to lift the injector needle up from the associated valve seat. This opening force counteracts a closing force that is exerted on the actuating part in the control pressure chamber. As long as the pressure in the control pressure chamber is kept at a high level, the closing force produced there is higher than the opening force acting on the injector needle so that the actuating part remains in the closed position and therefore the injector needle remains closed. On the other hand, if the pressure in the control pressure chamber and therefore the closing force produced there decreases, the opening force succeeds in moving the actuating part into the open position as a result of which the injector needle can lift up from the valve seat. Fuel can then be injected.
The pressure in the control pressure chamber is controlled by the control valve by virtue of the fact that the outlet is opened or closed. When the medium, usually fuel, supplied to the control pressure chamber is banked up due to the closing of the outlet, a high pressure is generated in the control pressure chamber which keeps the injector needle in a closed position. On the other hand, if the control valve opens the outlet, the pressure in the control pressure chamber decreases so that the injector needle can open.
The control valve according to the invention, has the advantage that an increased speed of the injector needle when opening is achieved. This is due to the fact that the cross section of the inlet is reduced by the actuating part when it moves from its closed position toward the open position. Consequently, a variable throttling of the inlet is achieved, which encourages the pressure drop in the control pressure chamber during the opening of the control valve so that less fuel can flow into the control pressure chamber.
According to a preferred embodiment of the invention, the mouth opening has a slot-shaped cross section. This embodiment has the advantage that the reduction of the inlet occurs in proportion to the movement of the actuating part in the control pressure chamber.